Study reveals leakage of carbon stored on land to aquatic environments

Fred Mackenzie, emeritus professor of oceanography at the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST), and colleagues from the Université Libre de Bruxelles, the University of Exeter, Laboratoire des Sciences du Climat et l’Environnement, and ETH Zürich, recently published a study in Nature Geoscience. The study showed, for the first time, that increased leaching of carbon from soil, mainly due to deforestation, sewage inputs and increased weathering, has resulted in less carbon being stored on land and more stored in rivers, streams, lakes, reservoirs, estuaries and coastal zones—environments that are together known as the “land-ocean aquatic continuum.”

“The budget of anthropogenic CO2 reported by the Intergovernmental Panel on Climate Change currently does not take into account the carbon leaking from terrestrial ecosystems to rivers, estuaries and coastal regions,” said Pierre Regnier from Université Libre de Bruxelles. “As a result of this leakage, the actual storage by terrestrial ecosystems is about 40 percent lower than the current estimates by the IPCC.”

“Carbon storage in sediments in these rivers and coastal regions could present a more secure environment than carbon stored in soil on land. As soil warms up, stored carbon can be lost to the atmosphere. The chances of this occurring in wet sediments are reduced,” said Pierre Friedlingstein from the University of Exeter.

A significant part of the carbon storage thought to be offered by ecosystems on land—mainly forests—is thus negated by this leakage of carbon from soils to aquatic systems, and to the atmosphere.